Does marriage make your bones grow stronger?

"Marriage really does make you stronger: Husbands have tougher bones than their single counterparts," reports the Mail Online – but apparently this only applies if the man marries after the age of 25.

The news stems from a study of 632 US men and women with an average age of 56. It examined their bone mineral density (BMD) and looked at the association between this and their marital status. BMD can be an important issue for older adults, as decreased BMD can increase the risk of developing osteoporosis.

The study found that men who were currently married without a history of divorce or separation had higher BMD than men with a more chequered relationship history. The average age men got married was 25, but men who got married younger than this also had a lower BMD.

Links were only found in men – strangely, no links between marital status and BMD were found in women, who are more at risk of osteoporosis than men.

This study certainly has curiosity value, but no causative link can be drawn between marriage and bone health. The authors speculate that being married long term may be less stressful than experiencing a divorce, separations or not being married at all, and that the lower stress levels are good for bone health. This is plausible, but was not proven by this research.

Bearing these limitations in mind, the study does highlight the possibility that what are usually considered to be purely physical conditions could be affected, at least partly, by mood and wellbeing.

Where did the story come from?

The study was carried out by researchers from the University of California, and was funded by the National Institutes of Health, the General Clinical Research Centers Program, and Jonsson Comprehensive Cancer Center at the University of California, Los Angeles.

It was published in the peer-reviewed medical journal Osteoporosis International.

The Mail took the study's findings at face value and should have considered its limitations. This research alone isn't enough to make firm conclusions, and the Mail's reporting, particularly its headline, didn't acknowledge this.

What kind of research was this?

This was a cross-sectional study using a group of US men and women who were part of an existing cohort study. It looked at the cross-sectional association between marital history and bone mineral density (BMD).

The researchers say that bone mass may be influenced by many psychosocial life stressors. They describe how previous research found that early life experiences – such as being in a secure financial environment as a child – influences adult body size and weight, which in turn can impact BMD in later life.

Various other studies have observed marriage to have possible protective effects on health. For example, married people have lower rates of chronic illness and physical disability. The researchers therefore aimed to explore its effects on BMD.

The study's cross-sectional assessment means it can only make observations and suggest associations. It cannot prove cause and effect.

What did the research involve?

The researchers looked for a link between marital status and BMD using 632 US adults. They took into account various socioeconomic, health and lifestyle factors known to influence bone density throughout life in an effort to isolate the effect of marriage.

The study used participants from the MIDUS National Study of Health and Well-Being, which recruited participants between 1995 and 1996. They were reassessed 9 to 10 years later between 2004 and 2006.

At this second assessment, just over a third of participants had clinical assessments of their medical history and had body measures taken, including BMD.

After excluding those taking medications that could affect their BMD (such as corticosteroids or osteoporosis medications), they were left with a sample of 632 people – 294 men and 338 women.

Marital status was assessed in both waves of the study. People were classed as:

currently married (current being the time of BMD assessment) and never before divorced, widowed or separated

currently married, but previously divorced, widowed or separated

currently divorced, widowed or separated

never married

Marital quality was also assessed by questioning how people thought their spouse felt about them and how close they felt their relationship was.

The researchers put participants into age categories (younger than 50, 50 to 60 and above 60). Various potential confounders were taken into account, including:

ethnicity

body weight

childhood socioeconomic status

educational level

smoking and alcohol intake

lifetime physical activity

menopausal information for women

What were the basic results?

The average age of participants was 56.5 years. Average age at first marriage was 25.6 years for men and 22.8 years for women. Women were less likely to be stably married (currently married with no previous separations: 34% of women versus 51% of men) and more likely to have been never married and have had marital disruptions (16% versus 11% of men).

Overall, currently married men had a higher BMD than all other marriage categories. Compared with married men with no previous divorces or separations:

men who were currently divorced, widowed or separated had a BMD 0.33 standard deviations lower

men who were currently married but previously divorced, widowed or separated had a BMD 0.36 standard deviations lower

men who had never married had a BMD 0.53 standard deviations lower

However, among men married at least once, every year they first married below the age of 25 was associated with a 0.07 standard deviation decrease in BMD. For example, men who married at 18 had lower BMD than those who married at 21, who had a lower BMD than those who married at 25.

No significant associations were seen between marital status and BMD in women. The only observation found for women was that greater perceived support from their spouse was associated with increased BMD. In men, there was no association between spouse support and their BMD.

How did the researchers interpret the results?

The researchers concluded that in men, marriage before the age of 25 and marital disruptions have a detrimental effect on bone health.

They say that marital quality is associated with better bone health in women.

Conclusion

No firm causative associations between marriage and bone health can be drawn from the results of this study alone. The study has a number of limitations to consider.

Although it was based on a cohort study that carried out two waves of assessments 10 years apart, for the purposes of the current study researchers assessed the current and previous marital status at the same time that they measured BMD. This makes it a cross-sectional assessment, which cannot prove cause and effect.

Although the researchers took into account various lifestyle and socioeconomic confounders that could have had an influence, there is likely to be a complex relationship between these factors, marital status and measures of health, and it is difficult to say whether their effect has been fully accounted for.

The sample size was small for a cross-sectional study at just 632 US adults, decreasing the reliability of the results, particularly when all the positive associations relate to even fewer than this (only 294 men).

Similarly, the average age of participants was 56.5, who first married around 30 years previously. The same relationship may not be seen in other samples of people of different cultures or ethnicity, or among younger people getting married today.

The fact that the observation was not found consistently in men and women may indicate that further exploration needs to be performed.

Although the research has found an association between marital status and higher BMD in men, we don't know whether the changes in BMD observed would have actually had any effect on the men's health or quality of life. For example, we cannot say whether lower BMD leads to men developing osteoporosis or being more at risk of fractures.

The study assessed marriage, but this was the most convenient way of measuring stable long-term relationships. The influence of any potential stress-related effect is unlikely to be linked directly to the institution of marriage itself, but rather the quality and duration of the partnership. A similar effect may have also been found in unmarried cohabiting couples, both straight and gay.

Proven ways to protect your bones are regular exercise and eating a healthy diet. Read more about bone health.